Due to the high-density integration of semiconductor devices in recent years, wiring and separation widths of circuit patterns required for producing semiconductor devices have become smaller. Typically, a circuit pattern is formed by etching a target film using a patterned mask.
To form a fine circuit pattern, it is necessary to reduce the minimum size of a mask pattern and to accurately transfer openings with small sizes to a target film.
However, when etching an organic mask made of, for example, an amorphous carbon layer film (which is hereafter referred to as an “ACL film”), “bowing”, where the cross section of a part of an opening of the ACL film widens, may occur. When bowing occurs, the ACL film being etched collapses and the opening is closed. This, for example, may result in a problem where a target film becomes unable to be etched.
Patent Document 1 discloses a technology for suppressing bowing by using an oxygen gas (O2) and a carbonyl sulfide (COS) gas as process gases.